Two isostructural mixed- valence vanadium phosphonoacetates H-2(DABCO)[(VO)-O-IV(H2O)V-III(OH)(O3PCH2CO2)(2)]center dot 2.5H(2)O (1) and H-2(PIP)[(VO)-O-IV(H2O)V-III(OH)(O3PCH2CO2)(2)]center dot 2.5H(2)O (2) have been synthesized. They crystallize in the orthorhombic space group Pnna with a) 7.0479(10) angstrom, b) 15.307(2) angstrom, and c) 17.537(3) angstrom for 1 and a = 7.0465(9) angstrom, b) 15.646(2) angstrom, and c = 17.396(2) angstrom for 2. X- ray single-crystal diffraction reveals that 1 and 2 have a three- dimensional open framework featuring 16- ring ellipsoid channels that are filled with doubly protonated 1,4- diazabicyclo[ 2,2,2] octanium/ piperazinium cations and water molecules. According to the classification in metal organic frameworks, 1 and 2 contain infinite (-O-V-)(infinity) chains that are cross-linked by "metalloligand" [VO(H2O)(O3PCH2CO2)(2)](4-) into a 3-D net of the sra topology. The temperature dependence of the magnetic susceptibility of 1 shows that the chi(m) T value in the range of 60 - 320 K is constant of 1.105 cm(3) K mol(-1)/V-2 unit, and upon further cooling, the chi(m) T value rapidly increases to 1.81 cm(3) K mol(-1) at 2 K. The corresponding effective magnetic moment (mu(eff))/V-2 unit varies from 2.97 mu(B) at 320 K to 3.80 mu(B) at 2 K. The magnetic data in the range of 2 - 320 K follow the Curie-Weiss law with C = 1.074 cm(3) K mol(-1) and Theta = -1.34 K.